The EU Water Framework Directive 2000/60 (Integrated River Basin Management for Europe) establishes the importance of preserving water quality through policies applied at watershed level given the strong links existing among ecological, hydrological, and hydrogeological systems. Therefore, monitoring campaigns of river water quality should be planned with multidisciplinary approaches starting from a landscape perspective. In this paper, the effects of the basin hydrology on the river water quality and, in particular, the impacts caused by the runoff production coming from agricultural areas are investigated. The fluvial segments receiving consistent amount of pollutant loads (due to the runoff routing over agricultural areas) are assumed more critical in terms of water quality and thus, they require more accurate controls. Starting from this perspective, to evaluate the runoff productions coming from agricultural areas, we applied a semi-distributed hydrological model that adopts satellite data, pedological and morphological information for the watershed description. Then, the river segments receiving critical amount of runoff loads from the surrounding cultivated areas were identified. Finally, in order to validate the approach, water quality for critical and non critical segment was investigated seasonally, by using river macroinvertebrates as indicators of water quality because of their effectiveness in preserving in time a memory of pollution events. Biomonitoring data showed that river water quality strongly decreases in correspondence of fluvial segments receiving critical amount of runoff coming from agricultural areas. The results highlight the usefulness of such a methodology to plan monitoring campaigns specifically devoted to non-point pollution sources and suggest the possibility to use this approach for water quality management and for planning river restoration policies.
Two hundred and fifty soles (30 g initial weight) were randomly stocked in 12 tanks (recirculation system) at two different stocking densities (2.3 and 1.3 kg m−2) and fed on two different diets (50% and 54% of crude protein and 21% and 18% of total lipid, respectively, for diets A and B) with triplicate tanks for treatment. The trial lasted for 300 days. Fish stocked at low density showed a significantly higher weight gain than the fish reared at 2.3 kg m−2 density (94.1±7.4 vs. 78.9±8.2 g, P<0.01) with a specific growth rate (SGR) of 0.46±0.11 and 0.43±0.16 (P<0.01) respectively. Feed conversion ratio (FCR) was more favourable for lower density groups (2.50 vs. 2.64, P<0.01). Diet B led to a higher final weight (124.1 vs. 110.2 g, P<0.01) and a better feed utilization (FCR: 2.49 vs. 2.65, P<0.01). Except for the lipid content, which was higher in the low‐density group (2.6% vs. 2.3%, P<0.05), proximate composition of sole's muscle was not influenced by treatments. Dover sole reared at low stocking density showed higher monounsaturated fatty acid (35.27% vs. 34.40%, P<0.01) and lower saturated fatty acid (24.36 vs. 26.13%, P<0.01) contents, and lower atherogenic (0.67 vs. 0.75, P<0.01) and thrombogenic (0.28 vs. 0.32, P<0.01) indexes.
Fundamentally, in land based mediterranean aquaculture, two techniques are applied to supply water with oxygen: paddling water aeration and application of pure oxygen. The two oxygenation techniques result in quite different PO2 regimens and, consequently, different fish growth performance and gill morphology.Data exist showing a reduction in total respiratory surface (RSA) and increasing gas diffusion distance (GDD) in gills of sea bass (Dicentrarchus labrax, L.) farmed under elevated PO2 regimens. That such a modification might have an effect on the ion regulation has been defined elsewhere as osmorespiratory compromise.In this study, European sea bass previously acclimatized to two PO2 regimens, mild hypoxia and mild hyperoxia (70-80% and 130-140% of the saturation value, respectively), were challenged for 1 hour with hypo-osmotic plus manipulation stress in two separate trials. During the first trial, when only Na + loss was determined, the ion efflux during the first 5 min resulted in a rate of 163.72±31 and 112.23±87 nmol g -1 min -1 from hypoxia and hyperoxia sea bass groups, respectively, and, if sustained, would approach 15.3 and 11.2% per hour of the total body Na + , respectively. During the second trial, in which both Na + and Clloss were determined, after 60 min the Na + loss was shown to be 76.86±12 and 179.28±32 nmol g -1 min -1 for the fish previously acclimatized to hyperoxia and hypoxia regimens, respectively, whereas for Clthis loss was 62.02±11 and 157.28±28 nmol g -1 min -1 , respectively. Our data are compatible with the hypothesis of an osmotic advantage of sea bass exposed to an elevated PO 2 regimen, achievable with application of pure oxygen, instead of simple water aeration.This work is licensed under a Creative Commons Attribution 3.0 License (by-nc 3.0).
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